In the fabrication of semiconductor chips, semiconductor wafers are divided into individual dies, which are then packaged into chips or otherwise mounted onto some intermediate carrier or printed circuit board. This process generally involves two steps, wafer dicing and wafer sorting. In general, wafer dicing involves sawing a wafer into individual dies. In preparation of the wafer dicing process, a wafer is mounted on a cutting ring, placed in a chuck face down, and wafer tape is stretched over the back of the wafer. The tape is evenly distributed onto the wafer using a roller device, and then excess tape is cut away from the ring. Thereafter, the wafer is mounted on chuck for dicing, wherein a diamond blade is used to cut the wafer into individual dies. With the dicing process, the wafer is cut into individual dies without cutting through the wafer tape so that the individual dies remain attached to the wafer tape after the dicing process. The diced wafer is then ready for a wafer sorting process where the individual dies are removed from the wafer tape.
Typically, a semi-automated or fully automated pick and place tool is used to separate the individual dies from the wafer tape. In general, pick and place tools operate by lifting an individual die from the wafer tape and placing the die onto a package, substrate, wafer or other dies (3-D package). With both types (semi-automated and fully automated) of pick and place tools, the wafer tape with the diced wafer is mounted to the tool such that the wafer tape is stretched over a frame. A soft vacuum collet is then placed against an individual die to be removed. Then, one or more eject pins push up through the wafer tape to elevate the die and loosen and dislodge the die from the tape. The vacuum collet then lifts the die from the tape and places the released die into a final package or in an intermediate carrier, for example. With a semi-automatic pick and place tool, a human operator manually turns a series of positioning (XY) knobs to center a target die in the crosshairs displayed on a monitor. The monitor allows the operator to position the pick-up collet over the center of the die. With an automated pick and place tool, the positioning (XY) and centering process is performed automatically using a pattern recognition system.
When using pick and pace tools as described above, significant bending forces can be exerted on a die as the eject pin presses up and the tape pulls down on the edges of the die. These bending forces can cause the die to crack or otherwise break. With semiconductor technologies that use SiGe substrates, or thinning of silicon wafers, the resulting semiconductor dies tend to be fragile. These thin, fragile dies are highly susceptible to cracking and damage due to bending forces exerted on the dies when being separated from wafer tape using conventional pick and place tape release techniques and tools.